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Biomedical subjects

G Macdonald

Publications and source records attributed to G Macdonald.

At least 19 recordsLinked to original sources
PubMed1995

Decontaminating dental instruments: testing the effectiveness of selected methods.

The decontamination of dental instruments before sterilization is designed to safeguard dental personnel from exposure to bloodborne pathogens and to remove gross contamination. The authors studied the relative effectiveness of decontamination methods that included ultrasonic cleaning, presoaking with an enzymatic cleaner and dishwashing. Results indicated that the most effective methods involved presoaking followed by cleaning. However, no single procedure eliminated detectable concentrations of blood contamination.

Analysis of Variance↗
PubMed1993

Metabolism of uridine in expanded extracellular volume states.

1. Uridine and uridine monophosphate (UMP) are natriuretic and a vasopressor in intact rats. In deoxycorticosterone acetate (DOCA)-salt hypertensive rats metabolic clearance rate (MCR) of uridine is raised and basal plasma uridine diminished, suggesting that metabolism of uridine is linked to changes in extracellular space. 2. Plasma uridine concentration was raised in 38 patients with chronic renal failure compared with age- and sex-matched healthy controls (8.49 mumol/L, 4.37-13.74 mumol/L median, interquartile range, and 2.64 mumol/L 2.51-2.74 mumol/L, respectively, P < 0.001). Plasma uridine was significantly diminished after isotonic fluid removal by ultrafiltration (UF) from 7.25 mumol/L (3.7-11.08) to 5.07 mumol/L (3.3-8.3), P < 0.001, whereas concentration of marker solutes urea and creatinine remained unchanged. During haemodialysis (HD), plasma uridine fell significantly from its pre-HD level. 3. In an animal model of expanded extracellular space the one-kidney, one-clip rat, plasma uridine was significantly higher (20.56 +/- 1.19 mumol/L, P < 0.01) and MCR diminished (34.93 +/- 3.44 mL/kg per min, P < 0.01) compared with sham-operated animals (plasma uridine 12.14 +/- 1.07 and MCR 53.59 +/- 4.11 mL/kg per min). Uridine or UMP did not inhibit Na+, K(+)-ATPase in either of the two assay systems. 4. It was concluded that catabolism of uridine is reduced by extracellular expansion and probably increased by volume reduction by UF.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1993

Metabolic studies of uridine in rats with DOCA-salt hypertension and on high sodium diet.

1. The steady-state metabolic clearance and calculated secretion rate of the pyrimidine nucleoside uridine were studied by equilibrium infusion in normal rats, rats on a high sodium diet, rats made hypertensive by subcutaneous injection of deoxycorticosterone acetate (DOCA), unilateral nephrectomy and high sodium drinking fluid, and two control groups of rats for the hypertensive group. 2. Basal plasma uridine concentration in DOCA-salt hypertension rats was found to be significantly reduced to 3.99 +/- 0.31 mumol/L (mean +/- s.e.m.) compared with control rats (11.98 +/- 1.64 mumol/L). Metabolic clearance (MCR) in DOCA-salt hypertensive rats was significantly raised (200.54 +/- 10.77 mL/kg per min) compared with control rats (65.17 +/- 1.99 mL/kg per min). No difference was found in plasma uridine concentration and MCR among the other two control groups and high sodium diet rats. Calculated secretion rate was unchanged in all animals. No significant differences were found between different groups of rats in blood pressure responses to uridine. 3. The raised metabolic clearance and reduced plasma uridine concentration in DOCA-salt hypertension may be consistent with increased intracellular transport and phosphorylation of uridine to the physiologically active compound uridine monophosphate (UMP) which would lead to arteriolar constriction, hypertension and natriuresis. The results contrast with those in humans with extracellular fluid (ECF) expansion from endstage renal failure and rats with one-kidney, one-clip (1K1C) hypertension but are not due to the pharmacological effects of deoxycorticosterone. The difference may be due to the haemodynamic consequences of reduced renal perfusion pressure or reduced renal mass compared with DOCA-salt model.

Animals↗
PubMed1991

Physical characteristics of the hand and early clinical skills. Their relationship in a group of dental hygiene students.

Twelve hand measurements were made on 45 first-year dental hygiene students within one week of their entering a dental hygiene program. Multiple regression was performed, using three clinical examinations (use of periodontal probe, use of 3-A explorer, and use of Gracey curets) as dependent variables, to assess whether or not hand measurements predicted early clinical skill development. None of the hand measurements were predictive for the explorer examination. Wrist width accounted for 13% of the variance on the probing examination and 24% of the variance on the curet examination. Finger span added 16% variance to the equation. A total of 40% variance was explained by these measures on the curet examination. Results suggest that wrist width and finger span may be important predictors of early dental hygiene clinical skill development.

Aptitude Tests↗
PubMed1990

Uridine kinase inhibition is involved in the vasodilator effects of minoxidil in the rat.

1. Since minoxidil is a pyrimidine derivative, its actions on vascular smooth muscle may derive from structural relationships to the uridine nucleotides, which have been shown to be vasoconstrictive in the rat. 2. Minoxidil at a low vasodepressor dose of 0.03 mg/kg per min abolished the pressor response to uridine at doses from 2 to 8 mumol/kg per min, but did not reduce the responses to uridine monophosphate or uridine diphosphate in similar pressor doses, suggesting an action on either transport of uridine into cells or on uridine kinase which catalyses phosphorylation of uridine to uridine monophosphate, the mediator of uridine's vascular actions. 3. The active metabolite of minoxidil was found to inhibit rat liver uridine kinase in vivo using an HPLC technique. 4. Plasma uridine concentration was significantly higher in 11 hypertensive patients on minoxidil compared with pretreatment values, suggesting that uridine kinase inhibition is of a degree sufficient to increase the circulating pool of uridine. 5. The data is consistent with uridine kinase inhibition being a mechanism for the vasodilator actions of minoxidil.

Animals↗
PubMed1987

Effect of nifedipine on carbohydrate metabolism and serum lipoproteins in hypertensive patients with and without diabetes mellitus.

Newly diagnosed hypertensive patients, and patients with hypertension which was not controlled by their existing therapy, were studied in a single-blind, placebo-controlled trial. Criteria for inclusion in the study were a systolic blood pressure less than 160 mmHg and a diastolic blood pressure greater than 95 mmHg. The study group was composed of 15 non-diabetic patients, 14 patients with non-insulin dependent diabetes mellitus (NIDDM) and 13 patients with insulin-dependent diabetes mellitus (IDDM). Mean supine and erect, systolic and diastolic blood pressure were reduced in all three groups after 2 and 14-16 weeks of nifedipine therapy (P less than 0.001). Mean fasting blood glucose, mean haemoglobin A1, mean total serum cholesterol, mean high density lipoprotein (HDL) cholesterol and mean serum triglycerides were not affected by nifedipine in any of the three groups over the 14-16 weeks' treatment. Forty out of the 42 patients entering, completed the study. One patient with NIDDM and angina died from a myocardial infarction in the final 4 weeks of the study, and one non-diabetic patient was unable to tolerate nifedipine after two weeks of treatment and was withdrawn from the study. No patients were withdrawn due to treatment failure.

Adult↗
PubMed1987

The use of nitrendipine in the treatment of elderly hypertensives.

The ability of nitrendipine to control blood pressure (BP) over a 24-hour period was assessed in elderly patients over 65 years of age with a systolic BP (SBP) greater than 170 mmHg, and a diastolic BP (DBP) greater than 100-130 mmHg. Twenty-two patients were randomized equally to two groups: group 1 received the drug once daily and group 2, twice daily. The study was double-blind, with patients in group 1 receiving a matching placebo tablet instead of the second dose of nitrendipine before retiring to bed. Patients attended the hospital clinic at 10 a.m. before taking their morning tablet, so that BP was recorded 24 hours (group 1) or 12 hours (group 2) after nitrendipine. The study design permitted one dose titration if the target SBP of less than 170 mmHg or DBP of less than 100 mgHg was not achieved after three weeks of active therapy; the dose was doubled and the patients received 6 weeks of therapy at the preferred dosage. Mean DBP after 6 weeks' nitrendipine was comparable in the two groups and significantly lower than that with placebo (P less than 0.001), but mean systolic BP was lowered only in group 2 patients (P less than 0.001). There was no significant difference in mean SBP or DBP between patients on 20 mg daily and 10 mg b.d. Therefore, in elderly patients, once daily nitrendipine controls DBP as satisfactorily as the same daily dose given in two divided doses, but does not reduce SBP as adequately.

Aged↗
PubMed1987

The uridine nucleotides constitute a natriuretic pressor system.

1. Uridine monophosphate was tested in the conscious rat for natriuretic properties and an immunoperoxidase technique was used to localize uridine-containing compounds in the rat kidney. 2. Uridine monophosphate, infused in a moderate pressor dose, caused a significant natriuresis compared to the effect of control infusions of solvent vehicle. 3. Uridine-containing compounds were found in most tubular elements with particularly dense staining in the distal and collecting tubules. 4. While the increased sodium excretion may have been due to increased renal perfusion pressure, the high density of uridine staining in distal nephrons suggests that the uridine nucleotides have a specific nephron function, possibly relating to sodium transport.

Animals↗